A difficulty in the development of ophthalmic diagnostic devices is obtaining information about the human eye, such as geometry, aperture diameter depth, etc. without incurring significant discomfort or injury to a human subject. The development of an ophthalmic diagnostic instrument requires repetitive gathering of information, and this can be painful and problematic for a human test subject.
An additional problem is the fact that the eye is a living organism and differs from one person to the next. Obviously, this compounds the problem of gathering accurate data about the eye geometry because there is no way to truly measure in-vivo tissue of the eye to the micron level without physically removing the eye.